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ECEG287 Optical Detection Course Notes Part 19: Conclusion

ECEG287 Optical Detection Course Notes Part 19: Conclusion. Profs. Charles A. DiMarzio and Stephen W. McKnight Northeastern University, Spring 2004. VIS= 0.40-0.75 μ. γ -Ray. RF. Electromagnetic Spectrum (by λ). UV= Near-UV: 0.3-.4 μ Vacuum-UV: 100-300 nm Extreme-UV: 1-100 nm.

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ECEG287 Optical Detection Course Notes Part 19: Conclusion

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  1. ECEG287 Optical Detection Course NotesPart 19: Conclusion Profs. Charles A. DiMarzio and Stephen W. McKnight Northeastern University, Spring 2004 DiMarzio & McKnight, Northeastern University

  2. VIS= 0.40-0.75μ γ-Ray RF Electromagnetic Spectrum (by λ) UV= Near-UV: 0.3-.4 μ Vacuum-UV: 100-300 nm Extreme-UV: 1-100 nm IR= Near: 0.75-2.5μ Mid: 2.5-30μ Far: 30-1000μ 10 nm =100Å 0.1 μ 1 μ 10 μ 100 μ = 0.1mm (300 THz) 0.1 Å 1 Å 10 Å 1 mm 1 cm 0.1 m X-Ray Soft X-Ray Mm-waves Microwaves DiMarzio & McKnight, Northeastern University

  3. What is Optical Detection? • The goal is to get information from light. • Usually we look for variations in the amount of light over • space... • or time... • or spectrum... • or some combination of these. • Generally the output is an electrical signal. • It may be digitized for use in a computer. • We need to measure this signal in the presence of noise. DiMarzio & McKnight, Northeastern University

  4. Course Overview 2. Sources and Radiometry 3. Noise 2-5. Detectors 6. Circuits 7. Coherent Detection 8. Signal Statistics 9. Array Detectors DiMarzio & McKnight, Northeastern University

  5. Some Detection Issues • Optics • Radiometry, Beam Shaping, and Filters • Detector Physics • Converting Optical Energy to Electrical • Receiver Circuit • Matching to Detector, Proper Biasing • Interpretation of Data • Dealing with Noise and Signal Statistics DiMarzio & McKnight, Northeastern University

  6. Spectral Response Modulation Response Responsivity Noise (NEP) Damage Level Sensitive Area Circuit Considerations Device-Specific Issues Filtering Angle, Position, Wavelength Packaging Window Transmission, Position Power Requirements Cooling/Vacuum Requirements General Detector Issues DiMarzio & McKnight, Northeastern University

  7. Square-Law Detector DiMarzio & McKnight, Northeastern University

  8. Noise Signal + Noise Ps Ps Pn DiMarzio & McKnight, Northeastern University

  9. Noise Issues • Optical Signal Power (Watts) • Normally Related to Some Desired Quantity (Reflectivity, Temperature, Distance, Magnetic Field, Scattering, Absorption, etc.) • NEP (Watts per root Hertz) • Can be Related to “NEX” • Example: NEDT DiMarzio & McKnight, Northeastern University

  10. Thermal Detectors Photon Detectors Two Basic Detection Concepts i/P Absorber hn e- Heat Sink l Photon Energy: E=hn=hc/l Total Energy: Pt Photon Count: np=Pt/hn Electron Count: ne=hqPt/hn Electron Rate: ne/t=hqP/hn Current: ene/t=(hqe/hn)P Power: P Heating: (dT/dt)H = CP Cooling: k(dT/dt)C =(T-Ts) Steady State: (T-Ts)/kC = P DiMarzio & McKnight, Northeastern University Stopped Mon 5 Jan 04

  11. Thermal Characteristics Wide Bandwidth Accuracy Examples Thermocouple Thermopile Pyroelectric Photon Characteristics Speed Sensitivity Examples Photoemissive Photoconductive -intrinsic & extrinsic Photovoltaic - intrinsic & extrinsic Detector Types DiMarzio & McKnight, Northeastern University

  12. Course Overview (1) • 3 - Noise and Photon Detectors • - Materials Considertations • (4) in Photoemissive Detectors • (5,6) in Semiconductor Detectors • 7 - Types of Semiconductor Detectors • 8 - P-N Junction Effects & Other Detectors • 9,10 - Detectors as Circuit Elements DiMarzio & McKnight, Northeastern University

  13. Course Overview (2) • 11,12 - Coherent Detection • 13 - Semiconductor Photoconductive Detectors • 14 - Signals and Noise • 15 - Intro to Arrays & a bit about color • 16 - Gain & BW in Semiconductor Dets. • 17 - Array Detectors • 18 - Odds and Ends DiMarzio & McKnight, Northeastern University

  14. SNR Layout for Coherent Detection PLO Filter? Amp Preamp Ps BPF PBKG DiMarzio & McKnight, Northeastern University

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